Audi RS4 GruppeM Intake VS. K&N Drop-In - European Car Magazine

You may recognize this car--we tested a K&N drop-in filter, MagnaFlow exhaust, Stratmosphere downpipes sporting high-flow cats and Revo software on it once before. With those mods power jumped from 321 whp to 341 whp (Feb. ’10).

Since then, the car’s been running great but the owner’s been thirsty for more. With only one aftermarket RS4 intake system available that we know of, we ordered a GruppeM Ram Air system from Modified by KC. Whether it would make any more power than the K&N drop-in we didn’t know (we didn’t think so), but we were curious enough to try. The trick with dyno testing an RS4 is in monitoring fluid, ambient and intake air temperatures, which have to be the consistent from run to run. This allows the ECU to trigger the same, and optimal, ignition timing and fuel mixtures. We monitored these parameters using an Actron Elite AutoScanner Pro CP9185 scan tool. Our scanner was also used to monitor temperatures during our 60-120mph pulls, ensuring accuracy, and the times were recorded using the GPS-based PerformanceBox from VBox USA.

Vehicle Data

Engine: 4.2-liter V8 FSI
Transmission: Six-speed manual
Mileage: 16,450
Current Modifications: Milltek/Stratmosphere downpipes, MagnaFlow cat-back exhaust, Revo Technik Stage 2 software, Continental ContiSportContact 3 tires, Forgestar F05 wheels
Dyno Data: Dynojet 424x
Temperature: 75-82 F
Humidity: 10-16%
Test gear: Third

Baseline
Peak power: 341.9 hp @ 7500 rpm
Peak torque: 296.7 lb-ft @ 3800 rpm
3000-8400 rpm dyno acceleration: 8.74 sec.
Temperature: 75 F
Humidity: 16%

Test Notes
To retest the K&N with the car’s current mods, we returned the intake back to its stock paper element for a new baseline. Like other newer cars, the RS4 goes through a lot of ECU adaptation on the dyno. With similar temps, the runs started off in the upper 320 whp range and finally reached the 340 range consistently, but not until after 10-12 runs. We knew we’d have to give several runs and about an hour’s worth of pulls for each upgrade when taking cool-down time into consideration.

This was the highest number we got so we went with it as our baseline. We were surprised to see almost the same horsepower we left off with from over a year ago, when we also had a K&N drop-in filter installed.

K&N Drop-in Filter

Test 1

Performance
Peak power: 352.7 hp @ 7200 rpm
Peak torque: 303.2 lb-ft @ 3800 rpm
Max horsepower gain: 16.0 @ 6700 rpm
Max torque gain: 12.5 lb-ft @ 6700 rpm
3000-8400 rpm accel.: 8.52 sec.
Temperature: 79 F
Humidity: 10%

Parts: K&N drop-in filter
Installation time: 0.5 hours
MSRP: $69

Pros

Cons

Test Notes
In Part 1 (Feb. ’10) we tested this K&N filter, only with the stock exhaust system and the Revo Stage 1 software. It netted a peak gain of 10.2 hp and 7.0 lb-ft of torque at 7500 rpm. This time, with the current exhaust mods and Stage 2 software, the filter was good for a little more power.

GruppeM Ram Air Intake

Test 2

Performance
Peak power: 361.1 hp @ 7500 rpm
Peak torque: 306.2 lb-ft @ 3700 rpm
Max horsepower gain: 12.1 @ 8300 rpm
Max torque gain: 7.6 lb-ft @ 8300 rpm
3000-8400 rpm accel.: 8.44 sec.
Temperature: 82 F
Humidity: 10%

Parts: Carbon-fiber airbox, conical filter, filter adaptor, machined MAF housing, stainless Allen bolt clamps, breather kit, mounting hardware
Installation time: 1.5 hours
MSRP: $1,695

Pros

Cons

Test Notes
These gains show the improvement over the K&N drop-in filter. Compared to stock, the peak gains were 21.5 hp at 8300 rpm and 15.1 lb-ft of torque at 6700 rpm.

As with the baseline and K&N runs, we had to give the car several runs to adapt to its new upgrade. Also, by now the ambient temperature had risen 6 degrees but the car still showed power gains.

After a few more pulls we actually saw a bit more power, but the data was discarded because it was while the car was being brought up to temp again, and the coolant and oil temperatures were still 10 degrees lower.

The icing on the cake is a new, unmistakable roar coming from new intake at all rpms.

Conclusion

Audi RS4s are very finicky on the dyno and must be run repeatedly before seeing usable numbers. Until then, power fluctuates, sometimes showing a loss.

At last, the K&N proved to be a great bang for the buck. But as it is with most cars, each additional horsepower gets more expensive. At least in the case of the GruppeM Ram Air intake, the average horsepower gain was double that of the drop-in filter, and nearly equaled all the previous exhaust and software mods combined in the top end.

To test the validity of the Ram Air designation, we also tested the car on the road, with the exact same starting point, ambient temperature and fluid and air temps. Sixty-120 mph runs with only a Third to Fourth gear shift was used for ease of repeatability. If the GruppeM was going to improve the ram-air effect, this test would show it.

With an average baseline of 10.92 seconds with the stock filter, the K&N drop-in improved this average to 10.85 seconds. The GruppeM averaged 10.64 seconds, nearly quadrupling the gain the K&N drop-in had over the stock setup.

For those unwilling to spend the GruppeM price, a K&N drop-in should surely find its way into every other RS4. But the GruppeM provides more power, more underhood bling, and an improved intake roar. Is it worth it? This owner sure thought so, and for the same reason he ponied up the extra $20K over the regular S4.

60-120 mph road test

(3rd-4th gear, two-run average)
Temperature: 64 F
Baseline: 10.92 sec.
K&N drop-in: 10.85 sec.
GruppeM Ram Air: 10.64 sec.

Revo Technik SPS
Revo Technik’s Stage 1 91-octane software took this car from a stock 321whp to 328 whp, with a peak gain of 13.5 hp and 13.0 lb-ft of torque at 6100 rpm and 5200 rpm, respectively.

MagnaFlow exhaust
The all-stainless MagnaFlow exhaust shaved 20 lb off the rear of the car and saw a good low-end gain, which peaked 8.6 hp and 12.5 lb-ft of torque at 3600 rpm. While peak power didn’t improve, the peak torque went up by 10 lb-ftfrom 276 to 286 lb-ft. The sound improved to a throaty V8 snarl as well.

Statmosphere’s Milltek downpipes with high-flow cats was good for an additional 10 lb-ft of torque, taking it to a peak 296 and the horsepower up a few more ponies, to 338. Peak gains were 9.4 hp and 10.7 lb-ft at 4000 rpm, and they shaved an additional 12 pounds of weight. By now the low- and mid-range gains were obvious during cruising, and the V8 roar had grown even deeper.

With Milltek downpipes and MagnaFlow exhaust in place, Revo’s George Osmun loaded up a new file, taking the car from 338 to 342 whp with Revo’s Stage 2 software. Peak gains were 7.7 hp and 4.9 lb-ft of torque at 8200 rpm.